Forensic Science in the 1920s
Source: Call of Cthulhu 7th Edition Investigator’s Handbook
7e Official
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Rule Summary
What forensic investigation methods and technologies were available to 1920s investigators vs modern capabilities.
Quick Reference Check:
Available: Fingerprints, ABO blood types, Ballistics comparison microscope, Chemical toxicology. Unavailable: DNA, digital search, luminol.
### Available 1920s Forensic Capabilities
1. **Fingerprints**: Widely accepted by 1920. Dusted with charcoal or aluminum powder and lifted with tape. Compared manually against physical card files (Henry System).
2. **Blood Typing (ABO System)**: Discovered in 1901. Can distinguish human blood groups (A, B, AB, O) to exclude suspects, but cannot identify individual DNA.
3. **Ballistics Comparison**: Comparison microscopes (invented 1925 by Goddard) allow forensic matching of bullet striations and firing pin marks to specific guns.
4. **Toxicology**: Reliable testing for arsenic, cyanide, strychnine, carbon monoxide, and heavy metals via organ tissue distillation.
5. **Photography**: Flash powder and tripod plate cameras used for documenting murder scenes and footprints.
### What Was NOT Available
- No DNA profiling or genetic testing.
- No electronic computer databases (searches take days of telegrams and manual ledger reviews).
- No instant radio dispatch for patrol cars (patrolmen check in via street corner callboxes).
- No luminol blood-reveal spray (invented in the late 1930s).